Old systems for making laminated shingles have generally required a number of interruptions in the flow of material from one work station to the next, and have necessitated a number of hand operations which have adversely affected the productivity of manufacturing plants making such roof coverings. In one such system, an apparatus is used to impregnate a fiber glass mat material with a waterproofing compound. Subsequently, one surface is covered with a bituminous adhesive material to which is adhered mineral granules to create a weather surface. The mineral granule coated shingle material continues to a work station where it is cut into a plurality of overlay portions and a plurality of underlay portions. In the case of one system the overlay members comprise a headlap portion and a butt portion. The butt portion thereof consists of a series of relatively randomly shaped tabs with spaces between these tabs. The spaces and tabs are dimensioned so as to permit pairs of overlay portions to be cut with the tabs thereof in an interleaved or interdigitated configuration. At a subsequent work station these overlay and underlay portions are separated from one another and are stacked or otherwise warehoused to await their subsequent lamination with the underlay portions.
Each underlay portion has a length approximately the same as that of the overlay portion and has a width so as to extend from the butt edge across the shingle to the portion approaching the headlap portion of the overlay portion when assembled in the finished shingle. This distance is usually less than the overall width of the overlay portion of the shingle. The underlay portion does not include interdigitated tabs since the underlay portion is a generally rectangular piece of composition shingle material which, when positioned beneath the overlay portion in the completed shingle, includes portions which are positionally aligned beneath the tabs of the overlay portion as well as portions which span the spaces between these tabs.
The overlay portions produced as above are withdrawn from stock and hand-fed onto one belt of a conveyor. This belt passes the overlay portion to a work station where adhesive material is applied to the lower face of the overlay portion along the tabs and along the upper edge of the butt portion. Simultaneously, underlay portions also withdrawn from stock are hand-fed to a work station where an apparatus indexes the underlay portions to a sprocket belt moving at a speed comparable to and along the same general path as the belt bearing the overlay portions past the adhesive applicating station. These two belts subsequently bring the overlay portion and underlay portion into intimate contact thus adhering the underlay portion to the underside of the overlay portion. The substantially completed laminated shingle continues on another conveyor to a work station which applies indicia for aiding in the application of the completed shingle to a roof structure, as well as applies a heat activatable resinous material to seal down the butt edges of the shingle when part of the completed roof shingle structure. Subsequently, shingles are collected at a third work station where shingles are stacked back-to-back and face-to-face to form a bundle of shingles for shipment to the ultimate consumer. The above-outlined process has in the past been successfully used to create a very popular roofing shingle for domestic use, namely the WOODLANDS shingle produced by the Johns-Manville Corporation, Denver, Colo. While the above manufacturing system has been able to produce the WOODLANDS shingle and successfully compete in the marketplace, it has had a number of drawbacks which have resulted in inhibiting the attainment of full productivity of the machinery used in manufacturing the shingle:
1. The prior art system required considerable warehousing and handling of completed underlay portions and overlay portions. Using conventional cutting and laminating machines, the rate at which overlay and underlay portions are produced differs considerably from the rate at which they can be laminated together to form a completed, laminated shingle. Hence, in order to complete the manufacture of a series of laminated shingles (each shingle comprising an overlay portion and an underlay portion) a supply of overlay portions and underlay portions must be accumulated. This accumulation must be produced, transferred to storage, transferred out of storage and inserted into a second production line. This material handling at each step requires a considerable number of hand operations. Such hand operations are inherently slower than the rate at which the finally collated underlay and overlay portions can be laminated together. Also such hand operations tend to be tedious, demeaning and subject to worker apathy, fatigue and hence error. The net result of this mismatch of production capabilities result in the reduction of productivity to about 1/3 to 1/5 of that achievable using the instant invention.
2. The prior art production system results in the laminating of underlay portions and overlay portions having different lengths. Presuming a 1/8" tolerance in the overall nominal 36" length for each of the underlay portions and overlay portions, the underlay portion may be as much as 1/4" longer or 1/4" shorter than its corresponding overlay portion. This problem has a further retarding effect on productivity. An explanation of the cause of this phenomenon and its effect will point up more clearly the magnitude of this problem and how the instant invention constitutes an improvement over this prior art system.
As was outlined above, the composition shingle material is rendered into the respective overlay portions and underlay portions at a cutting station. This cutting station included a cutter roll which rotates so that the blades positioned thereon have a tangential speed corresponding to the longitudinal speed of the composition shingle material. The cutter roll has blades projecting from its periphery which cut substantially through the composition shingle material to define the width (nominally 14" for the overlay portion and 7" for the underlay portion) and the length of either of these portions (nominally 36"). This cutting operation in more detail is done by pinching the composition shingle material as it moves between the cutter roll and a relatively smooth bias roll. The blades or the cutter roll wear rather quickly and can require replacing after only a few hours of operation. As these blades wear, the effective circumference of the cutter roll diminishes. This in turn causes the length of the shingle portions defined by the cutter roll to shorten proportionally. The conventional cutter system includes a variable ratio mechanical transmission which is operated to change (in this instance to decrease slightly) the rotational speed of the cutter roll in order to compensate for this phenomenon. The amount of speed change and its effect on length is determined by measuring the length of a sample shingle member. Also, as with any material, the composition shingle material has the capability of stretching along its length (depending on its composition, physical characteristics, etc.) when subjected to varying degrees of tension and as a result of the environmental conditions at the time of the cutting operations (i.e., temperature, humidity). Clearly, such a variation in length as the composition shingle material passes beneath the cutting blades of the cutter roll is minimized by careful control of production parameters (e.g., the variable ratio transmission mentioned supra, control of mat weight, composition, etc.). However, it has been found to be impractical to reduce any variation in length less than a nominal 1/8" variation from the ideal length. Thus it can be seen that in a given days output (or even in a single production run) there would be overlay portions having lengths up to 1/8" greater than the ideal length and also overlay portions being 1/8" shorter than the ideal length. Clearly this same phenomenon would affect the length of the underlay portions also.
When laminating the overlay portions to the underlay portions in this prior art system, there was no practical way of correlating undersized overlay portions with equally undersized underlay portions and oversized overlay portions with the equally oversized underlay portions. Hence, as stated above, it is quite possible to have a 1/4" difference in length of overlay portion and underlay portion in a shingle. While 1/4" in a 36" shingle could be said to affect the aesthetic function of the shingle, the primary disadvantage is that this error would create a considerable potential for leakage in a completed roof. In a given course of shingles in a completed roof, each shingle is placed end-to-end in the course forming a horizontal strip of shingles having, in the case of the WOODLANDS shingle, a series of generally randomly shaped tabs with spaces between the tabs. At the juncture between each shingle in each course, there is formed a vertical seam where the overlay portions are nailed in abutting relationship. The headlap portion of such shingles is covered by the next succeeding course of shingles. However, the underlay portion, if it is for example 1/4 " longer than the overlay portion, would tend to force this seam open by that 1/4". This would create a potential leakage problem if such a non-standard shingle was not eliminated at the factory or by the applicator.
Such variation in relative length of overlay portion and underlay portion in a shingle could cause an intolerable situation if permitted to be sold to the ultimate consumer for application on a roof structure. As is done, however such non-standard shingles are shunted from the production line before bundling and either become scrap or are corrected in some way by another hand or machine operation. In either event, such variation from an optimum shingle results in reduced productivity.
3. In the prior art system the hand feeding of overlay portions and underlay portions into the laminator machinery not only limits the rate in which the shingles can be laminated, but also increases the likelihood of damage to the shingle portions. One example of such production rate limiting and damage-prone operation is the hand feeding of underlay portions from the stack of underlay portions to the moving belt of the laminator apparatus. In this prior art system, stacks of underlay portions are fed to an apparatus which removes the bottom underlay portion from this hand fed stack and, using a pusher, places the individual underlay portion in position on the moving production belt. This operation of removing and positioning is done so that one underlay portion is provided for each overlay portion on the conveyor portion of the laminating apparatus. In order to maintain this one-to-one correlation, the conveyor includes positioning lugs which project from the surface of the belt and impact the individual underlay portions removed from the stack of underlay portions. These laminator belt lugs act to accelerate the otherwise statically positioned underlay portion to full belt speed in an almost instantaneous fashion. The need to accelerate a static underlay portion to the full belt speed at this work station sets an upper limit on as to how fast that belt speed can be. It has been found that this speed is about 150 to 225 feet per minute. Above this speed, depending on weight of the mat, temperature of the asphalt coating, etc., the impact of the lug on the trailing edge of the underlay member would cause a distortion of this trailing edge. Under certain conditions this distortion would either damage the underlay portion to an unacceptable extent or this distortion would aggravate the already bothersome problem of aligning the trailing edges of the underlay and overlay portions at the time of lamination.